It still sounds to me like a Faulty fuel pump.

But change motor anyway.

Mine had a faulty pump on 25000miles, 2004 model,6MT. It will run fine when started, driving fine until on temperature and heat are up in the engine bay and hotter time of the day.
It also then started to loose big power, if you put your foot down too much it wants to die, and if it idles it is all ok, then if you pull away, it feels the same as if you want to pull away in say, 4th or 5th gear, you can rev it but as soon as it starts to take (clutch) the revs and power will drop and you battle on like that.
I later listened good, windows closed and quiet and I could hear the fuel pump where I didnt hear it before, it had a whinning and hum through the body, just a bit.

The pump was replaced and I am now at about 7000miles, no problems.

After the motor change and still the same, let them do the pump, it is differant the pump works, it is speed regulated as well if I am correct. on Warrantee as it is expensive, they must replace the whole basket casing with pump / regulator unit. Here by us it will work out to about $1000 in your terms.

Good luck

Philip

 

^^ that sucks...the pump is about $160 US I think...and about 15min work to swap out